caiman

My Feedback: (1)

I bought the TM-8 and 608 receiver for my Futaba 9C radio. Installed it on my Hangar 9 1/5 scale Cessna 182 which has a Zenoah 26 gas engine. I configured the failsafe function so than the throttle would go to idle in case of a radio problem, and I made a range check on the ground.

I made three succesful flights, however two minutes after takeoff on my fourth flight the engine suddenly quit. The Zenoah 26 is of the magneto type and it did have a full fuel tankl, so it's very uncomoon for it to just quit being at half throttle. My theory is that for some reason the F/S function engaged and the sudden throttle cut made the engine quit (maybe the F/S idle was too low).

My questions are:

1)- Since I didn´t noticed any glitch on the airplane flight controls, how severe and long lasting should a signal glitch be in order for the F/S function to activate? is it possible that a less than a second glitch activated the F/S?

2)- Is it ok to tape the Fasst receiver antennas (the two antennas separate from each other and at 90°) to the fiberglass airplane fuselage, or should the receiving protion of the antennas be suspended in the air without touchin the fiberglass?

Thanks.

ira d

I have a Zenoah G26 and its not that uncommon for them sometime to
quit in flight, Its probably somthing to do with the engine not the radio.

caiman

My Feedback: (1)

Your words are very conforting! hehehe.

I have always thought that these engines were more reliable than the glow ones.

Could you tell me more about the conditions under which your engine have quit (Thorottle position, flight phase, etc.)?

What oil and oil ratio are you using? how did you adjusted the mixture (high and low)?

Do you have any idea of why they quit?

Thanks.

pilotpete2

!Hola,
I also have the TM-8 module and like it a lot. If you had actually had a failsafe in the radios system, all of your flight surfaces would have gone to the failsafe position, as the R608RF has FS on all channels, I'm really, really sure you would have noticed it if the radio had gone into failsafe.
I feel very sure that you had a simple dead stick. I set up my throttle failsafe on my R617RF to go to two clicks above normal idle, and I have tested it on the bench, no deadstick.
Best of luck,
Pete

ira d

I have noticed that the Zenoah engines can sometimes be running fine then you do
a loop or roll and they will just die Not just my engine but others all so.

For some reason and I dont really why but if I do roll in the first min or so after
take off my engine will die after that you can do anything you want and its fine.
Also when im ready to land if I throttle back to quick it may die otherwise it
runs great. The TM 8 has failsafe on all channels if you set it up so I think if the
radio went into failsafe you would have more going on than the engine dieing.

BobH

My Feedback: (2)

I'll postulate a theory for you about your (or any gas) engine. Even though the carb has a fuel pump on it that doesn't mean the fuel is getting drawn up onto the transfer ports to the top of the cylinder or even into the crank case. In order for that to happen there needs to be a good seal between the ring (or piston) and the cylinder walls. Vacumm is the key word here, more specifically crank case vacumm.
Whe the engine is first started and hasn't been run very much its not quite up to its full operating temp. The compression/vacumm is not optimal yet so a sudden change in attitude could disrupt the fuel/air mix movent.
Just my .02.

caiman

My Feedback: (1)

The weird thing here is that it was my fourth flight of the day and the engine didn't quit imediately after take off but about two minutes later.

ira d

I flew my G26 today first time in about a month,On my first flight about a min into
the flight I pulled the nose up vertical and the engine quit. But I made three more
flights and did loops rolls inverted flight and stall turns and the engine ran great.

Julez

...it appears, as if your reciever experienced a briev voltage dip below 3.8V.
In this case, throttle failsafe is activated.

pilotpete2

Hi Julez,
I had thought of that too, but, a throttle failsafe should not have resulted in a deadstick. If the throttle failsafe setting was in fact too low, it would be very easy to test this on the bench with the engine running at cruise power, then killing the transmitter, as far as I know the same FS value for throttle is used for low voltage warning and signal loss, again, easy to repeat on the bench.
Regards,
Pete

caiman

My Feedback: (1)

I had my G26 quit also and I think I had the failsafe throttle position too low.

Do you know how long a signal glitch should last in order to activate the F/S on a Fasst receiver (I didn´t noticed anything on the other channels)?

Julez

Um, ok, time for an english lesson
What exactly is a glitch, please? Servo movement without stick movement, stick movement without servo movement, or both? Or a general malfuction?

So, Caiman, your engine quit because of failsafe or other unknown reasons, and at the same time you lost control over your plane whatsoever?

Failsafe engages between 0.5 and 1sec of total absence of a signal, btw. I don't have the exact time at the top of my head.

caiman

My Feedback: (1)

Sorry for the spelling mistake, I am a Mexican citizen and trying to do my best writing in English (I bet your Spanish spelling is worse than my English! hehehe).

I think what happened on my airplane was that the radio signal was momentarly lost, I guess just by a fraction of a second since I didn't notice anything on the flight controls. Do you think a momentarly signal interruption (lasting maybe 0.5 sec) would engage the F/S?

Another hypothesis is that the engine quit for another reason (overheating, mixture, etc.).

Thanks.

Julez

I have to apologize. Your english is very good!
The remark about the english lesson was directed at me in a self-ironical way, as I am not totally sure what kind of problem the word "glitch" describes.

Ok, so you did not notice anything unnormal, despite that the engine quit?

Well, this of course can have multiple reasons. As you did not notice problems with the control of the plane, it seems unlikely that an engagement of failsafe cut the engine.

I can test the exact time tomorrow that it takes to engage failsafe.
You can also do it by yourself: Switch off the TX and check how long it takes until Failsafe engages.

Cheers,

Julian (not a word of Spanish, but my sister is pretty good at it :-) )

caiman

My Feedback: (1)

Thank you for your comments Julez. Don't worry, I don't speak any German either (it's harder than to fly a helicopter without a tail gyro).

Maybe it was an engine malfunction for some other reason. I will test it very well on the ground, double check the carb mixture, engine temperature, sparkplug, RPM, etc.

Other guys have mentioned on this forum that it's not that uncommon for these Zenoah engines to suddenly quit, I thought otherwise.